A number of different machines have been proposed to effect a compressive force on fibrous webs in order to impart pre-shrinkage properties to such material. One such apparatus is disclosed in U.S. Pat. Nos. 2,765,513 and 2,765,514 both to Walton which disclose application of compressive forces along short columnar lengths of a fabric. The machine disclosed, for imparting the compressive forces, utilizes two spaced rolls rotating in opposite directions at different speeds and between which a fabric is fed. A fabric indentor forces the fabric into the rubber surface of the faster rotating roll prior to the fabric being fed to the nip between the rolls with the result that a short columnar length of fabric between the indentor and nip is compressed. This apparatus has not been entirely successful in compressing all types of fabrics and in particular those falling into the knit category. In such knit fabrics yarns generally do not extend in lenghtwise or columnar directions; thusly, it becomes difficult to apply a compressive force to these yarns.
Other approaches have also been used to shrink such webs --for example rolls rotating in opposite directions at different speeds but utilizing a compactor shoe spaced from the faster roll rather than fabric indentors. In such instances, the faster moving roll acts as a feed roll to force a fabric material between it and the compactor shoe after which the material is fed to the nip between the rolls where the material is ironed to set the fibers or yarn in place. An example of this type of apparatus is shown in U.S. Pat. No. 3,015,145 to Cohn et al. A problem with apparatus of this type where opposed rolls rotating in opposite directions are utilized, as well as with the same type of apparatus described above using a fabric indentor, is that the faster rotating roll tends to scuff the material in the nip area making it difficult to treat such material uniformly on both sides.
Machines for effecting a compressive force on fibrous material have also utilized pairs of endless belts which are spaced from each other and which move in the same linear direction. The belts used are such that the linear speed of the surface of the belt may be changed by varying belt curvature with the result that when material fed between the belts is to be longitudinally compressed, the spacing between the belts is increased by decreasing the belt thickness which results in the surface speed of the belt being reduced so as to act as a retarding force on the material. The compressive effect utilizing belts however is limited by the belt thickness and construction. Further the belts are relatively expensive and require extensive maintenance.
To overcome certain of these deficiencies an apparatus is disclosed in U.S. Pat. No. 4,363,161 to Catallo wherein a fibrous web is forced into a stuffing chamber formed by a confining member having an apex and two movable surfaces with the apex extending into the space between the movable surfaces.
A further benefit may be achieved by utilizing, in association with the apparatus of U.S. Pat. No. 4,363,161 an impact blade which facilitates the flow of fibrous material around the apex of the confining member. One such apparatus is disclosed in U.S. Pat. No 4,447,938 and the impact blade is of concave guide surface configuration.
It has been found that such concave configuration of the impact blade provides drawbacks during operation as the edge of blade may disfigure the fabric.
Accordingly it is an object of this invention to provide the compressive shrinking apparatus contemplated herein with a new and improved impact blade to reduce substantially any fabric surface defects.
It is therefore another object of this invention to provide a higher grade fabric.
It is a further object of this invention to provide an apparatus for the compressive treatment of a wider variety of fibrous webs.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.